This document provides practicing engineers and building officials with a resource document for understanding the behavior of steel moment-frame buildings in earthquakes. It is one of the set of six State of the Art Reports containing detailed derivations and explanations of the basis for the design and evaluation recommendations prepared by the SAC Joint Venture. The recommendations and state of the art reports, developed by practicing engineers and researchers, are based on professional judgment and experience and supported by a large program of laboratory, field, and analytical research.
This report, FEMA-355D – State of the Art Report on Connection Performance, presents an overview of the current state of knowledge with regard to the cyclic inelastic behavior of beam-column connections that have been employed in moment-resisting steel frame structures in the past and that have been studied for potential use in such structures in the future. This state of the art report was prepared in support of the development of a series of Recommended Design Criteria documents, prepared by the SAC Joint Venture on behalf of the Federal Emergency Management Agency (FEMA) and addressing the issue of the seismic performance of moment-resisting steel frame structures. These publications include:
•FEMA-350 – Recommended Seismic Design Criteria for New Steel Moment-Frame
Buildings. This publication provides recommended criteria, supplemental to FEMA 302 – 1997 NEHRP Recommended Provisions for Seismic Regulations for New Buildings and other Structures, for the design and construction of steel moment-frame buildings and provides alternative performance-based design criteria.
•FEMA-351 – Recommended Seismic Evaluation and Upgrade Criteria for Existing Welded Steel Moment-Frame Buildings. This publication provides recommended methods to evaluate the probable performance of existing steel moment-frame buildings in future earthquakes and to retrofit these buildings for improved performance.
•FEMA-352 – Recommended Postearthquake Evaluation and Repair Criteria for Welded Steel Moment-Frame Buildings. This publication provides recommendations for performing postearthquake inspections to detect damage in steel moment-frame buildings following an earthquake, evaluating the damaged buildings to determine their safety in the postearthquake environment, and repairing damaged buildings.
•FEMA-353 – Recommended Specifications and Quality Assurance Guidelines for Steel Moment-Frame Construction for Seismic Applications. This publication provides recommended specifications for the fabrication and erection of steel moment frames for seismic applications. The recommended design criteria contained in the other companion documents are based on the material and workmanship standards contained in this document, which also includes discussion of the basis for the quality control and quality assurance criteria contained in the recommended specifications.
Detailed derivations and explanations of the basis for these design and evaluation recommendations may be found in a series of State of the Art Report documents prepared by the SAC Joint Venture in parallel with these design criteria. These reports include:
•FEMA-355A – State of the Art Report on Base Metals and Fracture. This report summarizes current knowledge of the properties of structural steels commonly employed in building construction, and the production and service factors that affect these properties.
•FEMA-355B – State of the Art Report on Welding and Inspection. This report summarizes current knowledge of the properties of structural welding commonly employed in building construction, the effect of various welding parameters on these properties, and the effectiveness of various inspection methodologies in characterizing the quality of welded construction.
•FEMA-355C – State of the Art Report on Systems Performance of Steel Moment Frames Subject to Earthquake Ground Shaking. This report summarizes an extensive series of analytical investigations into the demands induced in steel moment-frame buildings designed to various criteria, when subjected to a range of different ground motions. The behavior of frames constructed with fully restrained, partially restrained and fracture-vulnerable connections is explored for a series of ground motions, including motion anticipated at near-fault and soft-soil sites.
•FEMA-355D – State of the Art Report on Connection Performance. This report summarizes the current state of knowledge of the performance of different types of moment-resisting connections under large inelastic deformation demands. It includes information on fully restrained and partially restrained moment connections in welded and bolted configurations, based upon laboratory and analytical investigations.
•FEMA-355E – State of the Art Report on Past Performance of Steel Moment-Frame
Buildings in Earthquakes. This report summarizes investigations of the performance of steel moment-frame buildings in past earthquakes, including the 1995 Kobe, 1994 Northridge, 1992 Landers, 1992 Big Bear, 1989 Loma Prieta and 1971 San Fernando events.
•FEMA-355F – State of the Art Report on Performance Prediction and Evaluation of Steel Moment-Frame Buildings. This report describes the results of investigations into the ability of various analytical techniques, commonly used in design, to predict the performance of steel moment-frame buildings subjected to earthquake ground motion. Also presented is the basis for performance-based evaluation procedures contained in the design criteria documents, FEMA-350, FEMA-351, and FEMA-352.
In addition to the recommended design criteria and the State of the Art Reports, a companion document has been prepared for building owners, local community officials and other non-technical audiences who need to understand this issue. A Policy Guide to Steel Moment-Frame Construction (FEMA 354), addresses the social, economic, and political issues related to the earthquake performance of steel moment-frame buildings. FEMA 354 also includes discussion of the relative costs and benefits of implementing the recommended criteria.
Study of connection behavior is an important element of this project. The connection performance portion of the program focused upon the seismic capacity and behavior of connections. The work was coordinated by the Connection Performance Technical Advisory Panel (TAP). Numerous research teams participated in the connection performance effort. This report summarizes the work completed in this effort.
The connection behavior study included evaluation of connections used in the past for seismic design, the pre-Northridge connection with its welded-flange and bolted-web, and alternative connections which were developed to assure acceptable seismic performance. The evaluations comprised both experimental and analytical investigations. The completed work from these investigations is summarized here, and will be combined with the efforts of other teams within the SAC Steel Project. The other teams address a wide range of important issues material properties and behavior, inspection requirements, and welding electrodes and processes.
It is clear that while the connection performance work is an important part of the total program, it is not the only issue that must be evaluated for understanding the seismic performance of steel moment-frame buildings. This State of the Art Report has been developed as a comprehensive document. It must be comprehensive because a wide range of connections have been used and can be used for seismic design. A wide range of steel buildings can be constructed for very different seismic conditions. Except for a brief historical review, this report does not consider riveted connections or historic connection details because no damage was noted in these structures; nor are these alternatives expected to be used again in the future. Braced frame connections, column splices and foundation base connections are also beyond the scope of this study and this report. However, a wide range of bolted beam-column connections, welded-beam-column connections, welded-bolted beam-column connections, and alternatives which have evolved from the steel frame damage (and are in the public domain) are included in this study and this report. Several patented connections are discussed without details since complete information on their behavior is not publicly available. The report is also comprehensive in that it considers the range of performance levels from elastic behavior, through nonlinear behavior and inelastic deformation, and ultimately into deterioration and failure of the connection. The report and the study attempt to address all possible failure modes with each of these connections, since it is clear that many of these failure modes were not considered in past research efforts.
